The present invention relates to methods for lining pipes and connecting the lined pipe with adjacent or lateral pipes and particularly relates to methods for terminating liners to known dimensions to facilitate flanged or flared terminal connections with the adjacent or lateral pipes.
Methods for lining a host pipe, such as a concrete sewer line or a pressure pipe, with a thermoplastic liner are well known. One such system for lining pipes involves the manufacture of generally cylindrical pipe liners formed of extruded thermoplastic material. After extrusion, the cylindrical liners are shaped to reduce their cross-sectional envelope. Various methods and apparatus have been used to deform the initially extruded cylindrical liners into various cross-sectional configurations, for example, H, X, U and V cross-sections. A generally U-shaped liner, however, has been found to be most useful, practical and economical. Thus, the extruded cylindrical liner is shaped at the manufacturing site to a substantially reduced U-shaped cross-sectional configuration.
Subsequent to the manufacture of the deformed liner, the liner is typically coiled on a reel for transport to a job site. Alternatively, the deformed liner may be transported in linear lengths to the job site. At the job site, the deformed thermoplastic liner is conventionally pulled inside a pipe to be lined, i.e., a host pipe and the liner is then restored to its initially extruded cylindrical configuration with its outer cylindrical surface bearing against the interior cylindrical surface of the host pipe wall. The restoration of the deformed liner to its original cylindrical configuration is often carried out by the introduction of steam into the liner while in the host pipe whereby the liner is reformed to its cylindrical configuration and lines the host pipe. A well known system for lining pipes with a generally U-shaped liner which is reconfigured into a cylindrical liner upon installation is disclosed in various patents, namely U.S. Pat. Nos. 4,985,196; 4,863,365; 4,986,951; 4,998,871; 5,342,570; and 5,091,137, the subject matters of which are incorporated herein by reference.
To line underground pipes, particularly pressure pipes, i.e. pipes for transmitting fluid under pressure, it is important to provide terminal ends of the liner with known dimensions, e.g. inner and outer diameters and wall thicknesses. The dimensions of the liner when rerounded from the generally U-shaped configuration to a cylindrical configuration lining the host pipe cannot be controlled absent containment or constraints. Otherwise, the wall thickness of the uncontained and unconstrained liner will vary and the pipe may blow out entirely. Also, the inner and outer diameters of the liner cannot be controlled. It will be appreciated that the end of the liner must be flared or provided with known dimensions so that additional liner sections can be fused to the liner end. This is particularly important when lining pressure pipes which require the space between the inner diameter of the host pipe and the outer diameter of the liner to be sealed and particularly at the pipe joints. Otherwise the pressure of the fluid within the lined pipe could destroy the liner. Accordingly, there has developed a need for providing a method of terminating liners, preferably for underground pipe lines, which may or may not be pressure lines, to known dimensions such that flanged or flared terminal connections can be provided to adjacent or lateral pipes.